Multicomponent Self-Assembly of a Giant Heterometallic Polyoxotungstate Supercluster with Antitumor Activity

Lanthanide-Incorporated PIII-SbIII-Heteroatom-Templated Tetrahedral Heteropolyoxometalate Cluster for Detecting Early Tumor Marker MicroRNA-155

Heteropolyoxometalates have garnered widespread attention owing to their diverse structures and intriguing physicochemical properties. Herein, we successfully synthesized a unique lanthanide-incorporated PIII-SbIII-heteroatom-templated tetrahedral polyoxometalate cluster [H2N(CH3)2]20Na7H7{[Er6(H2O)6][W4O16][HPSbW15O54]4}·132H2O (1). The polyoxoanion of 1 can be perceived as four trilacunary Dawson [HPSbW15O54]11- {PSbW15} building blocks encapsulating a deca-nuclear heterometallic [Er6(H2O)6W4O16]10+ cluster. This heterometallic cluster comprises an inner tetrahedral [W4O16]8- ({W4}) core surrounded by an octahedral [Er6(H2O)6]18+ ({Er6}) shell. Consequently, the polyoxoanion of 1 exhibits the distinctive ({W4} ⊂ {Er6} ⊂ [{PSbW15}]4) three-shell structure. Considering the electron transfer characteristics of 1, it was coelectropolymerized with N-methylpyrrole (NMPy) to fabricate the 1-PNMPy film (PNMPy = polyNMPy). Notably, the incorporation of 1 improves the electron distribution within the PNMPy backbone, thereby narrowing the band gap of PNMPy and enhancing the conductive performance of the 1-PNMPy film. Therefore, the 1-PNMPy film is utilized as the modified electrode material to construct an electrochemical biosensor for the sensitive detection of the tumor marker microRNA-155. This research not only provides a viable approach for the fabrication of multishell heteropolyoxometalates but also promotes the exploration and application of multicomposition polyoxometalates in electrochemical biosensing microRNA.

Tailoring the dendronized structures of cyclodextrin-based supramolecular nanoassemblies for enhanced tumor paraptosis via disrupting endoplasmic reticulum homeostasis

Bioactive nanomaterials have been extensively utilized in medical applications. There are, however, very few reports on clinical applications of methylated β-cyclodextrin-derived supramolecular bioactive nanoagents, particularly in relation to the chemical features and biological properties. Herein, we designed and fabricated supramolecular bioactive nanoassemblies derived from permethyl β-cyclodextrin (PMCD) with increased proportions of PMCD on their dendronized side chains and further investigated the impact of chemical structures on their antitumor efficacy. Importantly, enhanced antitumor efficacy was observed with an increase in the proportion of PMCD on the dendronized side chains. Notably, pHPMA-co-(dendron Permethyl-β-CD4) (P4), which was featured with the highest PMCD proportion on its side chains, demonstrated the greatest potency in disrupting endoplasmic reticulum (ER) homeostasis, thus achieving conspicuous tumor cell paraptosis and promising antitumor efficacy in vivo without obvious side effects. Mechanistically, P4 colocalized with the ER, disrupted ER homeostasis, and triggered ER stress through the upregulation of proteins associated with the unfolded protein response, thus provoking abundant cytoplasmic vacuoles through the dilation of ER and resultant tumor paraptosis, a non-apoptotic mode of cell death. Overall, this study lays the groundwork for the precise design and synthesis of supramolecular bioactive agents derived from methylated β-cyclodextrin by precisely modulating their chemical structures. STATEMENT OF SIGNIFICANCE: Cyclodextrin-based supramolecular bioactive nanoagents could be employed for tumor management. However, there are challenges in developing β-cyclodextrin-derived bioactive nanoagents and tuning their structure-activity relationship to enhance their antitumor effects. Herein, we synthesized several bioactive nanoagents utilizing HPMA and PMCD by meticulously modulating their dendronized structures. It was revealed that P4, which was featured with the highest proportion of PMCD on its side chains, could distinctly interact with the ER. This enhanced interaction disrupted ER homeostasis, resulting in pronounced ER stress and paraptosis in tumor cells. Additionally, P4 exhibited efficient tumor retention and effective antitumor activity in vivo. This study demonstrated that biological function of β-cyclodextrin-derived bioactive nanoagents could be enhanced through optimization of the PMCD proportion on their side chains.

Stable Polyoxometalate-Based Metal-Organic Framework: Synthesis, Modification, and Catalytic Activity

Metal-organic frameworks (MOFs) with polyoxometalates (POMs) as the nodes usually feature a high stability. Those with available space and modifiable groups are expected to serve as a catalytic platform. In this work, a polyoxometalate-based metal-organic framework (POMOF)-bearing channel with a transversal surface of ca. 1.1 × 1.8 nm, [Ni(en)2]4H{[Ni6(tris)(en)3(SIP)1.5][B-α-PW9O34]}2·32H2O (1), was resulted by the collaboration of multiple ligands. The channel was lined with abundant amino groups that bonded with water molecules in it via hydrogen bonds. Compound 1 exhibited excellent thermal and chemical stabilities, which was confirmed by immersion experiments, in situ variable temperature powder X-ray diffraction, and reversible dehydration-hydration behavior. Pristine 1 showed remarkable activity in the hydrogen evolution reaction. According to the presence of amino groups in the channel, 1 was modified by Pd species. Resultantly, Pd was loaded into the channel successfully. The yielding material 1-Pd smoothly catalyzed the Suzuki-Miyaura coupling reactions.

A Highly Biocompatible Polyoxotungstate with Fenton-like Reaction Activity for Potent Chemodynamic Therapy of Tumors

Integrating Fenton chemistry and nanomedicine into cancer therapy has significantly promoted the development of chemodynamic therapy (CDT). Nanoscale polyoxometalates (POMs), with their reversible redox properties, exhibit promising potential in developing outstanding CDT drugs by exploring their Fenton-like catalytic reactivity in tumor environments. However, such research is still in its infancy due to the challenges of acquiring POMs that are both easily prepared and possess ideal therapeutic effects, physiological solubility, biocompatibility and safety. In this work, we report the synthesis of a new crystalline antimonotungstate {Dy2Sb2W7O23(OH)(DMF)2(SbW9O33)2} (1, DMF=N, N-dimethylformamide) with gram-scale high yield via a facile "one-pot" solvothermal reaction. 1 exhibits not only a soluble and water-stable POM nanocluster, but also excellent catalytic activity for hydroxyl radical-generating Fenton-like reactions. Further biomedical studies reveal that 1 can trigger cell apoptosis and promote lipid peroxidation, exhibiting high cytotoxicity and selectivity towards B16-F10 mouse melanoma cancer cells with an IC50 value of 4.75 μM. Especially, 1 can inhibit melanoma growth in vivo with favorable biosafety, achieving a 5.2-fold reduction in tumor volume and a weight loss of 76.0 % at the dose of 70 μg/kg. This research not only demonstrates the immense potential of antimonotungstates in CDT drug development for the first time but also provides new insights and directions for the development of novel anticancer drugs.

Naphthalenediimide-Based Hybrid Material with Eu-Substituted Polyoxometalate: Photochromism, Near-Infrared Photothermal Conversion, and C-3 Functionalization of Indoles

Designing and developing novel photochromic materials with additional functions such as photothermal conversion and photocatalysis are challenging but meaningful objectives. Crystalline naphthalenediimide (NDI)-based hybrids are an attractive class of multifunctional materials with fast-response photoinduced electron transfer and charge separation properties. They are promising photothermal conversion materials and photocatalysts. Herein, a novel hybrid material, EuPMo11O39(L)1.5(H2O)2]·DMA (EuMo-NDI) (L = N,N'-di(1-oxido-4-pyridyl)-1,4,5,8-naphthalenediimide), was prepared with a solvothermal method, integrating a photoactive NDI derivative and an Eu-substituted polyoxometalate. EuMo-NDI exhibits 0D structure with sensitive photochromic behavior under UV-vis light irradiation due to fast-response photoinduced electron transfer between its components. The colored EuMo-NDI sample demonstrated efficient near-infrared photothermal conversion due to the strong absorption of the photogenerated radical anion NDI•- and mixed valence heteropoly blue in the near-infrared region. Meanwhile, EuMo-NDI is easily excited in the presence of electron donors to form the radical species, which can activate inert O2 to superoxide radical O2•-. EuMo-NDI exhibited high photocatalytic activity for C-3 thiocyanation of indoles under mild conditions using white light as a driving force. This work provides an effective avenue to design novel photothermal conversion materials and photocatalysts using photochromic materials as platforms.

Syntheses and performance study of three POM-viologen compounds with photo- and electric-stimulation response

In recent years, stimulus responsive materials have received widespread attention. Under solvothermal conditions, three polyoxometalates-viologen organic-inorganic hybrid compounds were successfully constructed by combining a viologen ligand 1-(3-Nitro-benzyl)-[4,4']bipyridinyl-1-ium bromide (1,3-nibipy·Br) with octamolybdate, namely [Cu2(1,3-nibipy)4(H2O)2(β-Mo8O26)2]·2H2O (1), [Cu2(1,3-nibipy)4(H2O)4(β-Mo8O26)]·(β-Mo8O26) (2) and (1,3-Hnibipy)2·(β-Mo8O26) (3). These three compounds can exhibit color changing properties under both light and electrical stimulation. Through characterizations of PXRD, FT-IR, UV-vis spectra, XPS, EPR, CV, and other tests, the photochromic and electrochromic properties of these three compounds are caused by the generation of viologen radicals. Compounds 1-3 have a rapid photoresponse efficiency and can be made into mixed matrix films for use as ultraviolet detectors. In addition, coated filter paper synthesized from acetonitrile and compounds can serve as an innovative erasable ink-free printing material medium, which is suitable for various erasable ink-free printing and anti-counterfeiting fields. We further investigated the electrochromic devices prepared from compounds 1-3, which achieved color change at a voltage of around -0.2 V and exhibited good stability after 500 cycles.

A Two-Dimensional Layered Heteropolyoxoniobate Based on Cubic Sn(IV)-Containing {Sn12Nb56O200} Cages with Good Proton Conductivity Property

The first example of a Sn(IV)-containing heteropolyoxoniobate K6H18[Cu(en)2]8{[Sn(OH)2]12 (HNb7O22)8}·2en·88H2O (1) is built from nanoscale high-nuclearity cubic {[Sn(OH)2]12(HNb7O22)8} cluster and [Cu(en)2]2+ complexes. The cubic {[Sn(OH)2]12(HNb7O22)8} cage is composed of eight {Nb7O22} clusters and 12 SnO6 octahedrons. The eight {Nb7O22} fragments are situated at the vertices of the cubic cage, while the 12 SnO6 octahedrons are positioned along the edges of the cubic cage. The [Cu(en)2]2+ complexes link the {[Sn(OH)2]12(HNb7O22)8} clusters into two-dimensional (2D) (4,4) grid-like layers. The N-H···O hydrogen bonds between the [Cu(en)2]2+ complexes and the {[Sn(OH)2]12(HNb7O22)8} clusters link the layers to form a 3D supramolecular structure. Compound 1 exhibits a good proton conductivity of 3.1 × 10-2 S cm-1 at 85 °C and 98% relative humidity.

Multinuclear Antimony-Bismuth-Lanthanide Cluster-Connected Polyoxometalate for the Detection of 5-Hydroxyindoleacetic Acid via Luminescence

The judicious selection and combination of multicomponents provide great potential for the further exploration of new polyoxometalate (POM) materials. Here, a delicate control on tungstate, SbIII and BiIII sources, Eu3+ ions, and organic molecules led to the discovery of a novel multimetal cluster-embedded POM [H2N(CH3)2]9Na8H5{[Eu4(H2O)6Sb4Bi2W2O12](SbW9O33)2(SbW8O31)2}·78H2O (1). The polyoxoanion of 1 was constructed from four in situ-formed [SbW8O31]11- and [SbW9O33]9- building blocks connected by two hexa-metallic [Eu2(H2O)3Sb2BiWO6]9+ clusters, to be a rare member of Sb- and Bi-coexisting POM. The most impressive characteristic of 1 is the intricate [Eu2(H2O)3Sb2BiWO6]9+ cluster linker, which contains a SbIII-BiIII coinserted [Sb2BiWO6]3+ core grasping one [Eu1(H2O)2]3+ cation and one [Eu2(H2O)]3+ cation on both sides through Sb-O-Eu and Bi-O-Eu bonds. Functionalized by luminescence centers of Eu3+ ions, 1 can emit intense emission in water and be capable of detecting the biomarker of carcinoids, 5-hydroxyindoleacetic acid (5-HIAA) with a low limit of detection of 0.43 μM, high selectivity, and excellent anti-interference, as well as fast response (12 s). The high detectability of 1 for 5-HIAA is relevant to the underlying dynamic quenching and energy-transfer mechanism. In urine conditions, remarkable recognition of 1 for 5-HIAA and satisfactory recoveries were achieved, indicative of the possibility of 1 in detecting 5-HIAA in a real environment. This work reveals the special clustering effect of SbIII and BiIII atoms in the assembly of neoteric POM species and also promotes the application of POMs as potential diagnostic tool in the early detection of carcinoids.

Heterogeneous photocatalytic organic transformation using crystalline naphthalenediimide/perylenediimide-based hybrid materials

The use of light energy to drive photocatalytic organic transformations for the production of high-value-added organic compounds has garnered growing interest as a sustainable strategy for solving environmental problems and addressing the energy crisis. Naphthalenediimide (NDI) and perylenediimide (PDI)-based hybrid materials are highly regarded photocatalysts due to their strong visible-light absorption properties, highly electron-deficient aromatic cores, excellent redox activity, and tunable electrochemical and photochemical properties. However, although the design and preparation of NDI/PDI-based hybrid materials have progressed in the past few years, their application in photocatalytic organic reactions remains in the initial stage. This review highlights the recent research progress in NDI/PDI-based hybrid materials and their crystalline composites for photocatalytic organic transformations. In particular, the synthetic methods, structures, photochemical properties, and catalytic performance of NDI/PDI-based hybrid photocatalysts are illustrated to provide useful guidance for the further development and application of these materials.

Electrochemical Biosensor Based on Dual-Ligand Functionalized Lanthanide-Encapsulated Polyoxometalate Conductive Polymer Film for Detecting Broad-Spectrum Tumor Marker MicroRNA-155

In this work, a dual-ligand functionalized lanthanide-encapsulated selenotungstate [H2N(CH3)2]16Na2H10[Ho6(H2O)10(HPACA)4W10O28(Ac)2][SeW9O33]6 · 60H2O (1, HPACA = 2-pyrazinecarboxylic acid, HAc = acetic acid) was successfully acquired by simultaneously incorporating rigid HPACA and flexible Ac- ligands to one reaction system. Interestingly, the polyanion [Ho6(H2O)10(HPACA)4W10O28(Ac)2][SeW9O33]628- of 1 is composed of six trivacant Keggin-type [B-α-SeW9O33]8- units interconnected through an organic-inorganic hybrid dual-ligand bimetallic [Ho6(H2O)10(HPACA)4W10O28(Ac)2]20+ cluster. Moreover, the 1@PNMPy film (PNMPy = poly(N-methylpyrrole)) was successfully prepared through an electrochemical polymerization strategy. The doping of 1 significantly narrows the bandgap in the 1@PNMPy film, which enables the 1@PNMPy film to exhibit remarkable conductivity and rapid electron transfer capability. Then, the 1@PNMPy film-modified glassy carbon electrode was used to construct a 1@PNMPy-based electrochemical biosensor (ECBS), which achieves sensitive electrochemical detection (a low limit of detection of 0.108 fM and a wide concentration detection range of 10-8-10-15 M) for broad-spectrum tumor marker microRNA-155. Also, the 1@PNMPy-based ECBS has a good specific recognition performance for microRNA-155 in a variety of interfering media. The research not only contributes to a deeper understanding of the synthetic chemistry of multicomponent polyoxometalate (POM)-based materials but also can further expand innovative applications of multicomponent POM-based materials in electrochemical detection and electrochemical devices.

An injectable dual-layer chitosan-alginate nano-hydrogel incorporated Cu(I)-isopolymolybdate-based metal-organic framework tailored for three-in-one anti-cancer nanotherapy

Designing potential agents and constructing hydrophilic nano-hydrogel platforms for biomedical and pharmaceutical applications, especially for polyoxometalate-based metal-organic frameworks (PMOF), present both great desirability and significant challenges. A unique open porous Cu(I)-isopolymolybdate-based metal-organic framework (CCUT) has been self-assembled through ionothermal processes for in vivo synergistic anti-cancer therapy. The periodicity of Drugs@CCUT-1 (nano-crystals of CCUT after cation exchange and anti-cancer drugs upload) has been investigated by synchrotron wide-angle X-ray scattering, confirming the lattice structure unchanged. To mitigate toxicity, enhance stimuli-responsive drug delivery, hydrophilicity, and biocompatibility, an injectable dual-layer chitosan//alginate-based nano-hydrogel is developed to incorporate Drugs@CCUT-1. Potential interactions between the chitosan layer and the surface of CCUT-1 have been analyzed by Density Functional Theory (DFT). Furthermore, the nanoparticles Drugs@CCUT-1@Gel exhibit efficient type I photodynamic therapy (PDT) and chemodynamic therapy (CDT) within the bio-window, effectively eradicating tumors in deep tissue. CCUT-1 generates a substantial amount of reactive oxygen species (ROS), stimulating the Keap1-Nrf2 signaling pathway and resulting in the expression of phase II enzymes, typically HO-1. CCUT-1@Gel not only demonstrates high capacity for anti-cancer drug upload and release, but also exhibits strong synergistic CDT/PDT in vivo anti-tumor efficacy. Hence, CCUT-1@Gel represents a promising in vivo nano-platform for synergistic chemotherapy (CT)/CDT/PDT three-in-one anti-cancer approach.

Unprecedented Organogermanium Functionalized GeIV-SbIII-Templating Polyoxotungstate Nanocluster for Photothermal-Chemodynamic Cancer Therapy

The function-oriented synthesis of polyoxometalate (POM) nanoclusters has become an increasingly important area of research. Herein, the well-known broad-spectrum anticancer drug Ge-132 which contains GeIV as potential heteroatoms and carboxyl coordination sites, is introduced to the POM system, leading to the first organogermanium functionalized GeIV-SbIII-templating POM nanocluster Na4[H2N(CH3)2]16 H18[Sm4(H2O)12W4O14Ge(CH2CH2COOH)]2[SbW9O33]4[Ge(CH2CH2COOH) SbW15O54]2·62H2O (1). An unprecedented organogermanium templating Dawson-like [Ge(CH2CH2COOH)SbW15O54]12- building block is discovered. To take advantage of the potential pharmaceutical activity of such an organogermanium-functionalized POM cluster, 1 is further composited with gold nanoparticles (NPs) to prepare 1-Au NPs, which doubles the blood circulation time of 1-based nanodrug. Efficient separation of photogenerated charges in 1-Au NPs largely boosts the photothermal conversion efficiency (PCE = 55.0%), which is nearly 2.1 times that of either single 1 (PCE = 26.7%) or Au NPs (PCE = 26.2%), and simultaneously facilitate the generation of toxic activate reactive oxygen species in tumor microenvironment. Based on these findings, it is demonstrated that 1-Au NPs are a multifunctional and renal clearable nanomedicine with great potential in photoacoustic imaging guiding photothermal-chemodynamic therapy for breast cancer.

Pyrazine Dicarboxylic Acid and Phosphite-Bridging Lanthanide-Incorporated Tellurotungstates and Their Fluorescence Performances

Two pyrazine dicarboxylic acid and phosphite-bridging lanthanide-incorporated tellurotungstates [H2N(CH3)2]12 Na4[Ln4(H2O)2(H2PDBA)2(HPO3)2W6O10][B-α-TeW8O31]4 · 70H2O [Ln = Eu3+ (1), Tb3+ (2); H2PDBA = 2,5-pyrazine dicarboxylic acid) were prepared, which contain four [B-α-TeW8O31]10- subunits and a deca-nuclear heterometallic [Ln(H2O)2(HPO3)2 (H2PDBA)2(W3O5)2]24+ cluster. Strikingly, two H2PDBA ligands connect two equivalent {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moieties to form the polyanion skeleton, while the phosphite plays a bridging role in joining two lanthanide centers in the {W3Eu2O5(H2O)(B-α-TeW8O31)2(HPIIIO3)}8- moiety. In addition to the fluorescence (FL) properties of 1 and 2 at room temperature, their temperature-dependent FL properties were also investigated. In 80-298 K, FL intensities of 1 and 2 decrease as temperature increases, and their maximum relative sensitivities (Sr) are 3.70 and 1.99% K-1, whereas the minimum temperature uncertainties (δT) are 1.25 and 1.18 K for 1 and 2. In 298-973 K, upon increasing temperature, FL intensities of 1 and 2 initially rise to their maxima at 373 K and subsequently decrease. This is because samples of 1 and 2 undergo dehydration together with amorphization below 473 K and decomposition above this temperature. This work lays a foundation for the development for luminescent thermometers based on lanthanide-incorporated polyoxometalates.

Nicotinate-Modified Lanthanide-Substituted Selenotungstate and Its Catalase-like Activity for the Detection of H2O2 and Ascorbic Acid

A rigid nicotinate-modified lanthanide-substituted selenotungstate [H2N(CH3)2]6Na3H[La4SeW8(H2O)16(nica)2O28][SeW9O33]2·32H2O (1, Hnica = nicotinic acid) was synthesized and consists of two trivacant Keggin [B-α-SeW9O33]8- fragments and one unusual [SeW4O18]8- fragment bridged by a heterometallic [La4W4(H2O)16(nica)2O28]18- cluster. In the heterometallic cluster, two carboxyl O atoms in two nicotinate ligands directly coordinate with two W atoms in a stable C-O-W-O-W-O six-membered ring fashion. According to its catalase-like activity, 1 was utilized to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce blue oxidized TMB (ox-TMB), which can be used to establish a colorimetric sensing method for the detection of ascorbic acid. This work not only provides a promising platform for detecting H2O2 and ascorbic acid but also expands the application potential of polyoxometalate-based materials in biological and clinical analyses.

Modulated assembly and structural diversity of heterometallic Sn-Ti oxo clusters from inorganic tin precursors

Through modulating the multidentate ligands, solvent environments, and inorganic tin precursors during the synthesis processes, we have successfully prepared a series of unprecedented heterometallic Sn-Ti oxo clusters with structural diversity and different physiochemical attributes. Initially, two Sn6Ti10 clusters were synthesized using trimethylolpropane as a structure-oriented ligand and SnCl4·5H2O as a tin source. Then, when a larger pentadentate ligand di(trimethylolpropane) was used instead of trimethylolpropane and aprotic acetonitrile solvent was introduced into the reaction system, four low-nuclearity Sn-Ti oxo clusters were discovered, including two Sn1Ti1, one Sn2Ti2 and one Sn2Ti6. Finally, two mixed-valence state clusters, SnII4SnIV2TiIV14 and SnII4SnIV4TiIV20, were obtained by transforming the tin precursor from SnCl4·5H2O to SnCl2·2H2O and adjusting the acetonitrile solution with trace acetic acid/formic acid. Sn8Ti20 is the highest-nuclearity heterometallic Sn-Ti oxo cluster to date. Moreover, comparative electrocatalytic CO2 reduction experiments were carried out, and it was concluded that the Sn8Ti20-decorated electrode showed the most satisfactory performance due to the influence of mixed-valence states of the Sn atoms and the charging effects provided by 20 Ti4+ ions. This study presents important guiding significance for the design, synthesis and application optimization of functional heterometallic nanoclusters.

Indium-Assisted Construction of {SiNb18O54}-Based Aggregates and Their Assembly into Extended Polyoxoniobate Architectures

In this research, indium ions were introduced into polyoxoniobates (PONbs) reaction systems to facilitate the construction of different {SiNb18O54}-based aggregates, including an {In(en)2{SiNb18O54}2} (en = ethylenediamine) dimer, an {[InO2][In2(en)O3]2{SiNb18O54}3} trimer, and an {[In(en)2][InO2][In7(en)5O9]{SiNb18O54}4} tetramer. Interestingly, these aggregates were further assembled into three uncommon extended PONb architectures in the presence of [Cu(en)2]2+ complexes, namely, H3[Cu(en)2(H2O)][Cu(en)2]6[Cu(en)2]2{[In(en)2][K2{SiNb18O54}(H2O)6]2}·1.5en·16H2O, H9{[Cu(en)2]6{[Cu(en)2]3[Cu(en)2(H2O)][In(H2O)2][In2(en)(H2O)2(OH)]2{SiNb18O54}3}·5en·29H2O, and H14[Cu(en)2]0.5[Cu(en)2(H2O)]{[Cu(en)2]2{[Cu(en)2]3[Cu(en)2(H2O)]5[K(H2O)2][In(H2O)2][In(en)2][In7(OH)9(en)5]{SiNb18O54}4}·7en·39H2O. In addition, all of them have good water vapor adsorption capacities and moderate proton transport capabilities. The above results indicate that introducing suitable heteroatoms to induce the aggregation PONb building blocks and further assembling them into new structures is an effective strategy to enrich the PONbs' structural diversity and develop new functional materials.

Antitumor effects of a Sb-rich polyoxometalate on non-small-cell lung cancer by inducing ferroptosis and apoptosis

Polyoxometalates (POMs) are a class of anionic metal-oxygen clusters with versatile biological activities. Over the past decade, an increasing number of POMs, especially Sb-rich POMs, have been proven to exert antitumor activity. However, the antitumor effects and mechanisms of POMs in the treatment of non-small cell lung cancer (NSCLC) remain largely unexplored. This study employed a Sb-rich {Sb21Tb7W56} POM (POM-1) for NSCLC therapy and investigated its mechanism of action. Our results demonstrated that POM-1 exhibited cytotoxicity against H1299 and A549 cells with IC50 values of 3.245 μM and 3.591 μM, respectively. The migration and invasion were also inhibited by 28.05% and 76.18% in H1299 cells, as well as 36.88% and 36.98% in A549 cells at a concentration of 5 μM. In a tumor xenograft mouse model, POM-1 suppressed tumor growth by 76.92% and 84.62% at doses of 25 and 50 mg kg-1, respectively. Transcriptomic analysis indicated the alteration of ferroptosis and apoptosis signaling pathways in POM-treated NSCLC cells. Subsequent experimentation confirmed the induction of ferroptosis, evidenced by 5.6-fold elevated lipid peroxide levels with treatment of 5 μM POM-1, alongside increased expression of ferroptosis-associated proteins. Additionally, the apoptosis induced by POM-1 was also validated by the 19.67% and 30.1% increase in apoptotic cells in H1299 and A549 cells treated with 5 μM POM-1, respectively, as well as the upregulated activation of caspase-3. In summary, this study reveals, for the first time, ferroptosis as the antitumor mechanism of Sb-rich POM, and that synergism with ferroptosis and apoptosis is a highly potent antitumor strategy for POM-based antitumor therapy.

A Lanthanide-Incorporated Phospho(III)tungstate Aggregate Constructed from [HPIIIW8O31]10- and [W11O39]12- Building Blocks and Its Nanocomposite with CdS for Ultrasensitive Photoelectrochemical Detection of Oxytetracycline

A novel tartronic acid decorated hexa-CeIII-incorporated phospho(III)tungstate aggregate (C4H12NO)6Na18H2[(HPW8O31)2[W11O39]2(H2TAD)4(H2O)4W4Ce6H2P2O14]·84H2O (1, H3TAD = tartronic acid) was synthesized by a one-step assembly strategy. Its main skeleton is constructed from two [W11O39]12- fragments, two [HPIIIW8O31]10- segments and one H2TAD--ornamented dodecanuclear heterometallic [W4Ce6H2PIII2O14(H2TAD)4(H2O)4]18+ cluster. In the structure, the [HPIIIO3]2- groups not only work as the heteroatom template to induce the formation of lacunary [HPIIIW8O31]10- segments but also function as the connector to bridge Ce3+ cations. With the help of a reaction strategy of combining ultrasonication treatment with the continuous ion layer adsorption method, the 1/CdS composite was constructed and exhibits prominent photoelectrochemical activity. The 1/CdS composite was used as a photoelectrochemical sensor for oxytetracycline detection at 0 V (vs Ag/AgCl), which displays excellent properties with quick response and low limit of detection (0.042 nM). This work can provide some helpful references in the construction of novel PIII-induced polyoxometalates consisting of different building blocks and can extend the applications of polyoxometalate-based nanocomposites into photoelectrochemical detection for antibiotics as well as biomolecules.

Four polyoxomolybdated-based 3D compounds as supercapacitors and amperometric sensors

Four polyoxomolybdated compounds based on Tetp (Tetp = 4-[4-(2-Thiophen-2-yl-ethyl)-4H-[1, 2, 4]triazole-3-yl]-pyridine), namely [Zn(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Zn-Mo8), [Co(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Co-Mo8), [Cu4(Tetp)6(H2O)2]{H3[K(H2O)3](θ-Mo8O26)(Mo12O40)}·8H2O (Cu-Mo20) and [Cu3(Tetp)3][PMo12O40]·H2O (Cu-PMo12) are synthesized by hydrothermal methods and are used as electrode materials for supercapacitors(SCs) and electrochemical sensors. Inserting polyoxometalates (POMs) with redox active sites into transition metal compounds (TMCs) can improve the internal ion/electron transfer rate, thus effectively enhancing the electrochemical performance. Compared with the parent POMs, four compounds exhibit excellent electrochemical properties. In particular, Cu-PMo12 shows an excellent specific capacitance (812.3 F g-1 at 1 A g-1) and stability (94.42%), as well as a wide detection range (0.05 to 1250 µM) and a low detection limit (0.057 µM) for NO2- sensing.

An Organodiphosphate-Containing Polyoxoniobate Ring and Its Assembly into a Three-Dimensional Framework through Hydrogen Bonding

In this work, a novel organodiphosphate-containing inorganic-organic hybrid polyoxoniobate (PONb) ring {(PO3CH2CH2PO3H)4Nb8O16}4- (Nb8P8) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb8O36} motif and four {PO3CH2CH2PO3H} ligands. Interestingly, Nb8P8 can be joined together via K-H2O clusters {K2(H2O)4(OH)2} to form one-dimensional chains {[K2(H2O)4(OH)2]Nb8P8}n and further linked by {Cu(en)2}2+ (en = ethylenediamine) complexes, resulting in a three-dimensional supramolecular framework {[Cu(en)2]2[K2(H2O)4(OH)2]Nb8P8}·3en·H2O (1). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm3 g-1 (22.71 mol·mol-1) at 298 K, outperforming most of the known polyoxometalate-based materials. Impedance measurements prove that 1 can transfer protons with moderate conductivity. This study not only contributes to the structural diversity of organodiphosphate-containing PONbs and PONb rings but also provides a reference for the development of PONb-based materials with unique performance.

A series of viologen/POM materials with discoloration properties under the stimulation of X-ray, UV, electricity, and organic amines

At present, viologen-based compounds can undergo reversible chemical/physical changes under external stimuli such as light and electricity. This makes these compounds have potential applications in smart windows, displays, and sensors. In order to obtain such materials, three viologen-POM inorganic-organic hybrid compounds have been successfully synthesized by a hydrothermal method, namely {[Cu2(cybpy)8(α-P2W18O62)2}·18H2O (1), (Hbpy)·(cybpy)·[H4(α-P2W18O62)]}·32H2O (2) and {(Hcybpy)2(β-Mo8O26)}·2H2O (3) (cybpy·Br = 1-cyclobutylmethyl-[4,4']bipyridinyl-1-ium bromide, bpy = 4,4'-bipyridine). Three compounds exhibit good discoloration behaviors under various external stimuli, especially under the stimulation of X-ray, UV, electricity, and organic amines. In addition, in order to promote the compounds in the actual production of more applications, they were doped into the polymer matrix to construct hybrid films, which not only have the same response to external stimulation but also increase the repeatability of the photochromic process. Moreover, 1-3 powder samples in ethanol solution were ultrasonic treated and deposited on filter paper, which can be successfully used in erasable inkless printing.

Tetra-Ln3+-Implanted Tellurotungstates Covalently Modified by dl-Malic Acid: Proton Conduction and Photochromic Properties

Three unique dl-malic acid covalently modified tetra-Ln3+-implanted tellurotungstates [H2(CH3)2]9NaH9[Ln4(H2O)14W6O13(OH)5(Mal)2(B-α-TeW9O33)4]·48H2O [Ln = La3+ (1), Ce3+ (2), Pr3+ (3); H3Mal = dl-malic acid] were fabricated by reacting Na2TeO3, Na2WO4·2H2O, Mal, and LnCl3·6H2O with dimethylamine hydrochloride in an aqueous solution. The most prominent architectural feature of these compounds is the covalent connection mode of an organic ligand and a polyoxometallate backbone, which is relatively rare in the realm of polyoxotungstates. The tetrameric polyanion can be deemed as four [TeW9O33]8- fragments fused together via an intriguing hexanuclearity [W6O13(OH)5(Mal)2Ln4(H2O)14]13+ cluster. Impedance measurements manifest that all three complexes display splendid proton conduction properties, with an exceptional conductivity for 2 up to 2.48 × 10-2 S·cm-1 under 85 °C and 95% relative humidity. Moreover, compounds 1 and 3 exhibited fast reversible photochromic properties with allochroic half-life periods t1/2 of 1.046 and 0.544 min, respectively.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

An Innovative SbIII-WVI-Cotemplated Antimonotungstate with Potential in Sensing Paroxetine Electrochemically

Advances in polyoxometalate (POM) self-assembly chemistry are always accompanied by new developments in molecular blocks. The exploration and discovery of uncommon building blocks offer great possibilities for generating unprecedented POM clusters. An intriguing SbIII-WVI-cotemplated antimonotungstate [H2N(CH3)2]11Na[SbW9O33]Er2(H2O)2Sb2[SbWVIW15O57]·22H2O (1) was synthesized, which comprises a classical trivacant Keggin [SbW9O33]9- ({SbW9}) fragment and an unclassical lacunary Dawson-like [SbWVIW15O57]15- ({SbWVIW15}) subunit. Notably, the Dawson-like {SbWVIW15} subunit is the first example of a [SbO3]3- and [WVIO6]6- mixed-heteroatom-directing POM segment. Hexacoordinated [WVIO6]6- can not only serve as the heteroatom function but its additional oxygen sites can also link to lanthanide, main-group metal, and transition-metal centers to form the innovative structure. {SbWVIW15} and {SbW9} subunits are joined by the heterometallic [Er2(H2O)2Sb2O17]22- cluster to give rise to an asymmetric sandwich-type architecture. To further realize its potential application in electrochemical sensing, a conductive 1@rGO composite was obtained by the electrochemical deposition of 1 with graphene oxide (GO). Using a 1@rGO-modified glassy carbon electrode as the working electrode, an electrochemical biosensor for detecting the antidepressant drug paroxetine (PRX) was successfully constructed. This work can provide a viable strategy for synthesizing mixed-heteroatom-directing POMs and demonstrates the application of POM-based materials for the electrochemical detection of drug molecules.

The mechanism governing the formation of intermolecular charge transfer bands: a series of polyoxomolybdates as a case study

A series of proof-of-concept models of polyoxomolybdates with different protonated disubstituted aniline counterions and the same β-Mo8O26 polyanion were synthesized to study the mechanism governing the formation of the intermolecular charge transfer (inter-CT) band.

{Mo4}-directed structural evolution of highly reduced molybdenum red clusters for efficient proton conduction

A series of highly reduced Mo red clusters {Mo28} (1), {Mo30} (2), and {Mo40} (3) are synthesized from the rational assembly of planar {MoV4} building blocks and employed for proton conduction. 3 exhibits the best conductivity of 7.56 × 10-3 S cm-1 under optimal conditions due to the most efficient hydrogen-bonding network.

Four POM-Viologen Color-Changing Materials with Fast Color Response under Various External Stimuli

Four kinds of polyoxometalate (POM)-viologen compounds were synthesized by hydrothermal method, namely (1-cby)2·[H2(SiMo12O40)]·2H2O (1), (1-cby)2·[H2(SiW12O40)]·2H2O (2), (1-cby)2·(1,1'-bcby)2·{H4[Co4(H2O)2(PW9O34)2]}·12H2O (3), (1-cby)·(1,1'-bcby)·[H(α-PW11O39)CoII(1-cby)]·8H2O (4) (1-cby·Br = 1-Cyclopropylmethyl-[4,4']bipyridinyl-1-ium bromide, 1,1'-bcby·Br = 1,1'-Bis-cyclopropylmethyl-[4,4']bipyridinyl-1-ium bromide). These four POM-viologen compounds exhibit one-dimensional supramolecular network structures. Especially, compound 3 contains a rare sandwich POM subunit {Co4(H2O)2(PW9O34)2}10-. These four compounds can be used as color-changing materials, and they all exhibit noticeable color changes upon exposure to light, heat, and electricity. The discoloration mechanism involves viologen derivatives with electron-deficient properties accepting electrons from POM with electron-rich properties under external stimulation, leading to the formation of viologen free radicals. Among them, compounds 1 and 2 also have good properties for ink-free erasable printing, double anticounterfeiting, and ultraviolet detector because of their rapid color response to ultraviolet (UV) light. In addition, compounds 1-4 also show different color changes in the detection of volatile amines.

A tetrahedron-shaped polyoxoantimotungstate encapsulating a hexanuclear octahedral lanthanide-oxo cluster for an amperometric bromate sensor

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM-1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors.

Fullerene-like Niobovanadate Cage Built from {(Nb)V5 } Pentagon

The striking aesthetic appeal of fullerene-like clusters has captured the interest of researchers. Nevertheless, the assembly of fullerene-like polyoxovadanadate (POV) cages remains a significant challenge due to the scarcity of suitable pentagonal motif. Herein, we have successfully synthesized the first fullerene-like all-inorganic POV cage, {(V2 O)V30 Nb12 O102 (H2 O)12 } (V30 Nb12 ), by introducing Nb into the POVs. V30 Nb12 is assembled by 12 heterometallic {(Nb)V5 } pentagons through sharing V centers with Ih symmetry, reminiscent of C60 . To our knowledge, the fullerene-like V30 Nb12 not only represents the highest-nuclearity POV cage but also stands as the first niobovanadate cluster. Notably, V30 Nb12 exhibits excellent solution stability, as confirmed by ESI-MS, FT-IR and UV/Vis spectra. As there is no protection organic ligand on its outer surface, V30 Nb12 can be further modified with Cu-complexes to form a fullerene-like cluster based zigzag chain (Cu-V30 Nb12 ).

A Giant Heterometallic Polyoxometalate Nanocluster for Enhanced Brain-Targeted Glioma Therapy

Giant heterometallic polyoxometalate (POM) clusters with precise atom structures, flexibly adjustable and abundant active sites are promising for constructing functional nanodrugs. However, current POM drugs are almost vacant in orthotopic brain tumor therapy due to the inability to effectively penetrate the blood-brain barrier (BBB) and low drug activity. Here, we designed the largest (3.0 nm × 6.0 nm) transition-metal-lanthanide co-encapsulated POM cluster {[Ce10 Ag6 (DMEA)(H2 O)27 W22 O70 ][B-α-TeW9 O33 ]9 }2 88- featuring 238 metal centers via synergistic coordination between two geometry-unrestricted Ce3+ and Ag+ linkers with tungsten-oxo cluster fragments. This POM was combined with brain-targeted peptide to prepare a brain-targeted nanodrug that could efficiently traverse BBB and target glioma cells. The Ag+ active centers in the nanodrug specifically activate reactive oxygen species to regulate the apoptosis pathway of glioma cells with a low half-maximal inhibitory concentration (5.66 μM). As the first brain-targeted POM drug, it efficiently prolongs the survival of orthotopic glioma-bearing mice.

Polyoxometalates as Potential Artificial Enzymes toward Biological Applications

Artificial enzymes, as alternatives to natural enzymes, have attracted enormous attention in the fields of catalysis, biosensing, diagnostics, and therapeutics because of their high stability and low cost. Polyoxometalates (POMs), a class of inorganic metal oxides, have recently shown great potential in mimicking enzyme activity due to their well-defined structure, tunable composition, high catalytic efficiency, and easy storage properties. This review focuses on the recent advances in POM-based artificial enzymes. Different types of POMs and their derivatives-based mimetic enzyme functions are covered, as well as the corresponding catalytic mechanisms (where available). An overview of the broad applications of representative POM-based artificial enzymes from biosensing to theragnostic is provided. Insight into the current challenges and the future directions for POMs-based artificial enzymes is discussed.

Highly Efficient Oxygen Reduction N-Doped Carbon Nanosheets Were Prepared by Hydrothermal Carbonization

A metal-free carbon catalyst is a kind of oxygen reduction catalyst with great prospects. It is an important material with potential to replace the traditional Pt catalyst. In this paper, a kind of irregular and ultra-thin carbon nanosheet (K180M-300-900) with high catalytic activity was synthesized by hydrothermal calcination using okra as a biomass and NH4Cl as an N source. The prepared nitrogen-doped metal-free catalyst with high pyridine-N and graphitic-N provides an extremely large number of active sites and has certain lattice defects. Ultra-thin carbon nanosheets promote sufficient contact between the catalyst and electrolyte, promote the diffusion of oxygen, and result in a faster transfer rate of electrons. The initial potential and half-slope potential of K180M-300-900 are 0.99 V and 0.82 V, respectively, which are comparable to those of 20% Pt/C. In addition, the stability and methanol tolerance of this catalyst (K180M-300-900) are better than 20% Pt/C, so it has great development potential and application value. This result provides a new method to prepare metal-free carbon materials that will take the place of traditional Pt catalysts.

A series of isopolymolybdate-viologen hybrids with photo-, thermo- and electro-chromic properties

The combination of electron-deficient viologen ligands with electron-rich POMs is a typical acceptor-donor system that has recently received much attention. Under solvothermal and hydrothermal conditions, by introducing three symmetric viologen ligands into POM-based hybrid materials, we successfully constructed four POMs-viologen inorganic-organic hybrid compounds, namely (1,3-bcbpy)2·(δ-Mo8O26) (1) (1,3-bcbpy·2Cl = 1,1'-bis(3-carboxybenzyl)-4,4'-bipyridine dichloride), {CoII(1,4-bcbpy)2(H2O)2[H2(β-Mo8O26)]}·2H2O·2CH2O (2), (1,4-bcbpy)2·(δ-Mo8O26)·2H2O (3) (1,4-bcbpy·2Cl = 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridine dichloride, CH2O = formaldehyde), and {CuII(1,1-pmbby)2(H2O)[H2(β-Mo8O26)2]}·5H2O·C2H7N (4) (1,1-pmbby·2Cl = 1,1'-[1,4-phenylbis(methylene)]bis-(4,4'-bipyridine)dichloride, C2H7N = dimethylamine). These four compounds exhibit different fascinating structures, especially compound 4 is a typical metal-organic framework. Compounds 1-4 exhibit good discoloration behaviors under various external stimuli. For example, compounds 1-4 showed a positive response to the irradiation from a 300 W Xe lamp. When a positive voltage was applied to the ECD based on compounds 1-4, 1/2/3/4-ECD underwent a significant color conversion. What's more, compound 4 also showed obvious discoloration results after heating. In a word, 1-4 are multifunctional discoloration materials under different external stimuli. In addition, the coated filter paper prepared based on compound 3 can be used as a new printing material medium and can be successfully applied in erasable inkless printing and dual anti-counterfeiting.

Enhanced catalysis of a vanadium-substituted Keggin-type polyoxomolybdate supported on the M3O4/C (M = Fe or Co) surface enables efficient and recyclable oxidation of HMF to DFF

In the reaction of oxidizing 5-hydroxymethylfurfural (HMF), attaining high efficiency and selectivity in the conversion of HMF into DFF presents a challenge due to the possibility of forming multiple products. Polyoxometalates are considered highly active catalysts for HMF oxidation. However, the over-oxidation of products poses a challenge, leading to decreased purity and yield. In this work, metal-organic framework-derived Fe3O4/C and Co3O4/C were designed as carriers for the vanadium-substituted Keggin-type polyoxomolybdate H5PMo10V2O40·35H2O (PMo10V2). In this complex system, spinel oxides can effectively adsorb HMF molecules and cooperate with PMo10V2 to catalyze the aerobic oxidation of HMF. As a result, the as-prepared PMo10V2@Fe3O4/C and PMo10V2@Co3O4/C catalysts can achieve efficient conversion of HMF into DFF with almost 100% selectivity. Among them, PMo10V2@Fe3O4/C exhibits a higher conversion rate (99.1%) under milder reaction conditions (oxygen pressure of 0.8 MPa). Both catalysts exhibited exceptional stability and retained their activity and selectivity even after undergoing multiple cycles. Studies on mechanisms by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy revealed that the V5+ and Mo6+ in PMo10V2, together with the metal ions in the spinel oxides, act as active centers for the catalytic conversion of HMF. Therefore, it is proposed that PMo10V2 and M3O4/C (M = Fe, Co) cooperatively catalyze the transformation of HMF into DFF via a proton-coupled electron transfer mechanism. This study offers an innovative approach for designing highly selective and recyclable biomass oxidation catalysts.

A Forceful "Dendrite-Killer" of Polyoxomolybdate with Reusability Effectively Dominating Dendrite-Free Lithium Metal Anode

In this work, a series of Mo-containing polyoxometalates (POMs) modified separators to inhibit the growth of lithium dendrites, and thus improving the lifespan and safety of the cells is proposed. When the deposited lithium forms dendrites and touches the separator, the optimized Dawson-type POM of (NH4 )6 [P2 Mo18 O62 ]·11H2 O (P2 Mo18 ) with the stronger oxidizability, acts like a "killer", is more inclined to oxidize Li0 into Li+ , thus weakening the lethality of lithium dendrites. The above process is accompanied by the formation of Lix [P2 Mo18 O62 ] (x = 6-10) in its reduced state. Converting to the stripping process, the reduced state Lix [P2 Mo18 O62 ] (x = 6-10) can be reoxidized to P2 Mo18 , which achieves the reusability of P2 Mo18 functional material. Meanwhile, lithium ions are released into the cell system to participate in the subsequent electrochemical cycles, thus the undesired lithium dendrites are converted into usable lithium ions to prevent the generation of "dead lithium". As a result, the Li//Li symmetrical cell with P2 Mo18 modified separator delivers exceptional cyclic stability for over 1000 h at 3 mA cm-2 and 5 mAh cm-2 , and the assembled Li-S full cell maintains superior reversible capacity of 600 mAh g-1 after 200 cycles at 2 C.

A Coordination-Driven Self-Assembly and NIR Photothermal Conversion Study of Organometallic Handcuffs

Due to their fascinating topological structures and application prospects, coordination supramolecular complexes have continuously been studied by scientists. However, the controlled construction and property study of organometallic handcuffs remains a significant and challenging research subject in the area of supramolecular chemistry. Hence, a series of tetranuclear organometallic and heterometallic handcuffs bearing different size and metal types were rationally designed and successfully synthesized by utilizing a quadridentate pyridyl ligand (tetra-(3-pyridylphenyl)ethylene) based on three Cp*Rh (Cp* = η5-C5Me5) fragments bearing specific longitudinal dimensions and conjugated planes. These results were determined with single-crystal X-ray diffraction analysis technology, ESI-MS NMR spectroscopy, etc. Importantly, the photoquenching effect of Cp* groups and the discrepancy of intermolecular π-π stacking interactions between building block and half-sandwich fragments promote markedly different photothermal conversion results. These results will further push the synthesis of topological structures and the development of photothermal conversion materials.

Cerium-Encapsulated SbIII-SeIV-Templating Polyoxotungstate for Electrochemically Sensing Human Multidrug Resistance Gene Segment

A tower-like SbIII-SeIV-templating polyoxotungstate [H2N(CH3)2]12Na7H3[Ce0.5/Na0.5(H2O)5]2[SbSe2W21O75]2·50H2O (1) was synthesized, whose skeleton is assembled from two prolonged lacunary Dawson [SbSe2W21O75]13- units and two [Ce0.5/Na0.5(H2O)5]2+ linkers. The uncommon [SbSe2W21O75]13- unit can be viewed as a combination of one [SeW6O21]2- group grafted onto a trivacant Dawson [SbSeW15O54]11- subunit. The conductive composite 1-Au@rGO containing 1, gold nanoparticles, and reduced graphene oxide (rGO) was conveniently prepared, using which the 1-Au@rGO-based electrochemical genosensor was constructed for detecting human multidrug resistance gene segment. This work enriches structural types of dual-heteroatom-inserted polyoxometalates and promotes the application of polyoxometalates in genosensors.

Nanomaterial with Core-Shell Structure Composed of {P2W18O62} and Cobalt Homobenzotrizoate for Supercapacitors and H2O2-Sensing Applications

Designing and preparing dual-functional Dawson-type polyoxometalate-based metal-organic framework (POMOF) energy storage materials is challenging. Here, the Dawson-type POMOF nanomaterial with the molecular formula CoK₄[P₂W₁₈O₆₂]@Co₃(btc)₂ (abbreviated as {P₂W₁₈}@Co-BTC, H₃btc = 1,3,5-benzylcarboxylic acid) was prepared using a solid-phase grinding method. XRD, SEM, TEM et al. analyses prove that this nanomaterial has a core-shell structure of Co-BTC wrapping around the {P₂W₁₈}. In the three-electrode system, it was found that {P₂W₁₈}@Co-BTC has the best supercapacitance performance, with a specific capacitance of 490.7 F g^-1 (1 A g^-1) and good stability, compared to nanomaterials synthesized with different feedstock ratios and two precursors. In the symmetrical double-electrode system, both the power density (800.00 W kg^-1) and the energy density (11.36 Wh kg^-1) are greater. In addition, as the electrode material for the H₂O₂ sensor, {P₂W₁₈}@Co-BTC also exhibits a better H₂O₂-sensing performance, such as a wide linear range (1.9 μM-1.67 mM), low detection limit (0.633 μM), high selectivity, stability (92.4%) and high recovery for the detection of H₂O₂ in human serum samples. This study provides a new strategy for the development of Dawson-type POMOF nanomaterial compounds.

Structural Evolution and Properties of Praseodymium Antimony Oxochlorides Based on a Chain-like Tertiary Building Unit

Unveiling the structural evolution of single-crystalline compounds based on certain building units may help greatly in guiding the design of complex structures. Herein, a series of praseodymium antimony oxohalide crystals have been isolated under solvothermal conditions via adjusting the solvents used, that is, [HN(CH2CH3)3][FeII(2,2′-bpy)3][Pr4Sb12O18Cl15]·EtOH (1) (2,2′-bpy = 2,2′-bipyridine), [HN(CH2CH3)3][FeII(2,2′-bpy)3]2[Pr4Sb12O18Cl14)2Cl]·N(CH2CH3)3·2H2O (2), and (H3O)[Pr4Sb12O18Cl12.5(TEOA)0.5]·2.5EtOH (3) (TEOA = mono-deprotonated triethanolamine anion). Single-crystal X-ray diffraction analysis revealed that all the three structures feature an anionic zig-zag chain of [Pr4Sb12O18Cl15−x]n as the tertiary building unit (TBU), which is formed by interconnections of praseodymium antimony oxochloride clusters (denoted as {Pr4Sb12}) as secondary building units. Interestingly, different arrangements or linkages of chain-like TBUs result in one-dimensional, two-dimensional layered, and three-dimensional structures of 1, 2, and 3, respectively, thus demonstrating clearly the structural evolution of metal oxohalide crystals. The title compounds have been characterized by elemental analysis, powder X-ray diffraction, thermogravimetric analysis, and UV-Vis spectroscopy, and the photodegradation for methyl blue in an aqueous solution of compound 1 has been preliminarily studied. This work offers a way to deeply understand the assembly process of intricate lanthanide-antimony(III) oxohalide structures at the atomic level.

Constructing a Photocatalyst for Selective Oxidation of Benzyl Alcohol to Benzaldehyde by Photo-Fenton-like Catalysis

A photoactive metal-organic framework (MOF), [K(H₂O)][Cu(DPNDI)][Cu(DPNDI)(CH₃CN)(H₂O)] [Cu_1.5(DPNDI)_1.5H_1.5P₂W₁₈O₆₂]·2H₂O (Cu(Ι)W-DPNDI), was prepared by combining a functional photosensitizer N, N'-bis(4-pyridylmethyl)naphthalene diimide (DPNDI), copper(I) ions, and an oxidation catalyst [P₂W₁₈O₆₂]^6- into a single framework via a hydrothermal process. Cu(Ι)W-DPNDI exhibited a stable structure, strong light absorption capacity, a suitable band gap, and photoelectric properties, which provided favorable conditions for photocatalysis. In the confined space, the well-aligned Cu(I) ions and POM polyanions played a synergetic effect in the electron-transfer process and reactive oxygen species generation. By coupling photocatalysis and heterogeneous Fenton-like catalysis, Cu(Ι)W-DPNDI displayed high efficiency for the selective oxidation of aromatic alcohols, with up to >99% selectivity and 75% yield.

Polyoxometalates Impact as Anticancer Agents

Polyoxometalates (POMs) are oxoanions of transition metal ions, such as V, Mo, W, Nb, and Pd, forming a variety of structures with a wide range of applications. Herein, we analyzed recent studies on the effects of polyoxometalates as anticancer agents, particularly their effects on the cell cycle. To this end, a literature search was carried out between March and June 2022, using the keywords "polyoxometalates" and "cell cycle". The effects of POMs on selected cell lines can be diverse, such as their effects in the cell cycle, protein expression, mitochondrial effects, reactive oxygen species (ROS) production, cell death and cell viability. The present study focused on cell viability and cell cycle arrest. Cell viability was analyzed by dividing the POMs into sections according to the constituent compound, namely polyoxovanadates (POVs), polyoxomolybdates (POMos), polyoxopaladates (POPds) and polyoxotungstates (POTs). When comparing and sorting the IC₅₀ values in ascending order, we obtained first POVs, then POTs, POPds and, finally, POMos. When comparing clinically approved drugs and POMs, better results of POMs in relation to drugs were observed in many cases, since the dose required to have an inhibitory concentration of 50% is 2 to 200 times less, depending on the POMs, highlighting that these compounds could become in the future an alternative to existing drugs in cancer therapy.

Single-Crystal Superstructures via Hierarchical Assemblies of Giant Rubik's Cubes as Tertiary Building Units

Intricate superstructures possess unusual structural features and promising applications. The preparation of superstructures with single-crystalline nature are conducive to understanding the structure-property relationship, however, remains an intriguing challenge. Herein we put forward a new hierarchical assembly strategy towards rational and precise construction of intricate single-crystal superstructures. Firstly, two unprecedented superclusters in Rubik's cube's form with a size of ≈2×2×2 nm³ are constructed by aggregation of eight {Pr₄ Sb₁₂ } oxohalide clusters as secondary building units (SBUs). Then, the Rubik's cubes further act as isolable tertiary building units (TBUs) to assemble diversified single-crystal superstructures. Importantly, intermediate assembly states are captured, which helps illustrate the evolution of TBU-based superstructures and thus provides a profound understanding of the assembly process of superstructures at the atomic level.

Discovery and Isolation of Two Arsenotungastate Species: [As4W48O168]36- and [As2W21O77(H2O)3]22

Two novel arsenotungstate species, [As₄W₄₈O₁₆₈]^36- (1a) and [As₂W₂₁O₇₇(H₂O)₃]^22- (2a), have been successfully isolated under a one-pot synthetic method. 1a is the second largest arsenotungstate cluster and is constructed from four {AsW₁₂} clusters combined together. 2a can be described as lacunary sites of {As₂W₁₉} filled by {W₂O₈} units. Compounds 1 and 2 exhibit proton conductivity properties, and the conductivity value of 1 is 5.0 × 10^-3 S cm^-1 at 98% relative humidity and 75 °C. This work proves that the lattice water molecules and polyoxoanions can participate in the formation of a hydrogen bond, acting as effective pathway for intermolecular proton conduction.

Structurally-New Hexadecanuclear Ni-Containing Silicotungstate with Catalytic Hydrogen Generation Activity

A structurally-new, carbon-free hexadecanuclear Ni-containing silicotungstate, [Ni₁₆(H₂O)₁₅(OH)₉(PO₄)₄(SiW₉O₃₄)₃]^19-, has been facilely synthesized using a one-pot, solution-based synthetic method systematically characterized by single-crystal X-ray diffraction and several other techniques. The resulting complex works as a noble-metal-free catalyst for visible-light-driven catalytic generation of hydrogen, by coupling with a [Ir(coumarin)₂(dtbbpy)][PF₆] photosensitizer and a triethanolamine (TEOA) sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of 842 was achieved for TBA-Ni₁₆P₄(SiW₉)₃-catalyzed hydrogen evolution system. The structural stability of TBA-Ni₁₆P₄(SiW₉)₃ catalyst under photocatalytic conditions was evaluated by the mercury-poisoning test, FT-IR, and DLS measurements. The photocatalytic mechanism was elucidated by both time-solved luminescence decay and static emission quenching measurements.

First Ultrathin Pure Polyoxometalate 2D Material as a Peroxidase-Mimicking Catalyst for Detecting Oxidative Stress Biomarkers

Although two-dimensional (2D) materials with ultrathin geometry and extraordinary electrical attributes have attracted substantial concern, exploiting new-type 2D materials is still a great challenge. In this work, an unprecedented single-layer pure polyoxometalate (POM) 2D material (2D-1) was prepared by ultrasonically exfoliating a one-dimensional (1D)-chain heterometallic crystalline germanotungstate Na₄[Ho(H₂O)₆]₂[Fe₄(H₂O)₂(pic)₆Ge₂W₂₀O₇₂]·16H₂O (1) (Hpic = picolinic acid). The 1D polymeric chain of 1 is assembled from particular {Ge₂W₂₀}-based [Fe₄(H₂O)₂(pic)₆Ge₂W₂₀O₇₂]^10- segments through bridging [Ho(H₂O)₆]³⁺ cations. 2D-1 is formed by π-π interaction driving force among adjacent 1D polymeric chains of 1. Also, the peroxidase-mimicking properties of 2D-1 toward detecting H₂O₂ were evaluated and good detection result was observed with a limit of detection (LOD) of 58 nM. Density functional theory (DFT) calculation further confirms that 2D-1 displays outstanding catalytic activity and active sites are located on Fe centers and Hpic ligands. Under the catalysis of uricase, uric acid can be transformed to allantoin and H₂O₂, and then, H₂O₂ oxidizes TMB to its blue ox-TMB in the presence of 2D-1 as a catalyst. Then, we utilized this cascade reaction to detect uric acid, which also exhibits prominent results. This research opens a door to prepare ultrathin pure POM 2D materials and broadens the scope of potential applications of POMs in biology and iatrology.

Space-Confined Nucleation of Semimetal-Oxo Clusters within a [H7P8W48O184]33- Macrocycle: Synthesis, Structure, and Enhanced Proton Conductivity

Spatially confined assembly of semimetallic oxyanions (AsO₃^3- and SbO₃^3-) within a [H₇P₈W₄₈O₁₈₄]^33- (P₈W₄₈) macrocycle has afforded three nanoscale polyanions, [{As^III₅O₄(OH)₃}₂(P₈W₄₈O₁₈₄)]^32- (As₁₀), [(Sb^IIIOH)₄(P₈W₄₈O₁₈₄)]^32- (Sb₄), and [(Sb^IIIOH)₈(P₈W₄₈O₁₈₄)]^24- (Sb₈), which were crystallized as the hydrated mixed-cation salts (Me₂NH₂)₁₃K₇Na₂Li₁₀[{As^III₅O₄(OH)₃}₂(P₈W₄₈O₁₈₄)]·32H₂O (DMA-KNaLi-As₁₀), K₂₀Li₁₂[(Sb^IIIOH)₄(P₈W₄₈O₁₈₄)]·52H₂O (KLi-Sb₄), and (Me₂NH₂)₈K₆Na₅Li₅[(Sb^IIIOH)₈(P₈W₄₈O₁₈₄)]·65H₂O (DMA-KNaLi-Sb₈), respectively. A multitude of solid- and solution-state physicochemical techniques were employed to systematically characterize the structure and composition of the as-made compounds. The polyanion of As₁₀ represents the first example of a semimetal-oxo cluster-substituted P₈W₄₈ and accommodates the largest As^III-oxo cluster in polyoxometalates (POMs) reported to date. The number of incorporated SbO₃^3- groups in Sb₄ and Sb₈ could be customized by a simple variation of Sb^III-containing precursors. Encapsulation of semimetallic oxyanions inside P₈W₄₈ sets out a valid strategy not only for the development of host-guest assemblies in POM chemistry but also for their function expansion in emerging applications such as proton-conducting materials, for which DMA-KNaLi-As₁₀ showcases an outstanding conductivity of 1.2 × 10^-2 S cm^-1 at 85 °C and 70% RH.

Lanthanide-Anderson Polyoxometalates Frameworks: Efficient Sulfide Photooxidation

Three polyoxometalate-based metal-organic frameworks were synthesized by the thermal reaction of pyridyl-Anderson polyoxometalate linker and lanthanide ions. With the help of [Ru(bpy)₃]²⁺ photosensitizer, these frameworks exhibited excellent photocatalytic sulfide oxidation performance with sulfoxide selectivity. The reactive oxygen species as well as the photooxidation mechanism were also explored.